The present invention relates to an electrophotographic image forming apparatus and more particularly to a color image forming apparatus capable of accurately detecting positional deviation between images of different colors and correcting the deviation.
The prerequisite with a tandem image forming apparatus extensively used today is that images of different colors be brought into accurate register. Positional deviation between images of different colors is ascribable to various causes including skew, deviation in the subscanning direction, irregular pitch in the subscanning direction, magnification error in the main scanning direction, and deviation in the main scanning direction. While various schemes have heretofore been proposed for obviating positional deviation, none of them can accurately detect deviation to a satisfactory degree.